| 摘要 |
PURPOSE:To obtain a pulse width modulation signal without using a carrier signal, by negative-feeding back a fundamental wave component of an output signal to an input so that this feedback signal always follows a reference signal. CONSTITUTION:A negative feedback circuit is constituted of a comparator and an LPF. In case when the comparator has a hystereses characteristic, the polarity of output voltage generated in a terminal 2 is switched to positive from negative when voltage of a signal (called a deviation signal) Ve of a difference between a reference signal Vs and a feedback signal Vf has become higher than hysteresis voltage Vh, or to negative from positive when voltage of the deviation signal Ve has become lower than hysteresis voltage -Vh, and a pulse width modulation signal Vo following the reference signal Vs is obtained. Since this signal Vo cannot be compared directly with the reference signal Vs, a fundamental wave component of the signal Vo is fetched through the LPF, is negative-fed back as a feedback signal Vf, and a differnce Ve=Vs-Vf from the reference signal Vs is obtained. |
